Mongo DB , Spring boot : Exception opening socket , Caused by: Connection refused

I am using Spring Boot to connect to MongoDB but it is giving me an exception while trying to connect, the weird thing is that this was working for me before and suddenly it started giving me this error. Could anyone please help me out if this is the issue due to some another service is running on this port(27017), if so how could I found out that.

com.mongodb.MongoSocketOpenException: Exception opening socket
at com.mongodb.connection.SocketStream.open(SocketStream.java:63) ~[mongodb-driver-core-3.4.2.jar:na]
at com.mongodb.connection.InternalStreamConnection.open(InternalStreamConnection.java:115) ~[mongodb-driver-core-3.4.2.jar:na]
at com.mongodb.connection.DefaultServerMonitor$ServerMonitorRunnable.run(DefaultServerMonitor.java:113) ~[mongodb-driver-core-3.4.2.jar:na]
at java.lang.Thread.run(Thread.java:745) [na:1.8.0_45]
Caused by: java.net.ConnectException: Connection refused: connect
at java.net.DualStackPlainSocketImpl.waitForConnect(Native Method) ~[na:1.8.0_45]
at java.net.DualStackPlainSocketImpl.socketConnect(DualStackPlainSocketImpl.java:85) ~[na:1.8.0_45]
at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:345) ~[na:1.8.0_45]
at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206) ~[na:1.8.0_45]
at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188) ~[na:1.8.0_45]
at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:172) ~[na:1.8.0_45]
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392) ~[na:1.8.0_45]
at java.net.Socket.connect(Socket.java:589) ~[na:1.8.0_45]
at com.mongodb.connection.SocketStreamHelper.initialize(SocketStreamHelper.java:57) ~[mongodb-driver-core-3.4.2.jar:na]
at com.mongodb.connection.SocketStream.open(SocketStream.java:58) ~[mongodb-driver-core-3.4.2.jar:na]
... 3 common frames omitted

application.properties:

    spring.data.mongodb.host=localhost
    spring.data.mongodb.port=27017
    spring.data.mongodb.database=swt

pom.xml:

    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-data-mongodb</artifactId>
    </dependency>
    <dependency>
        <groupId>org.mongodb</groupId>
        <artifactId>mongo-java-driver</artifactId>
        <version>2.12.3</version>
    </dependency>

Read more here: https://stackoverflow.com/questions/47067871/mongo-db-spring-boot-exception-opening-socket-caused-by-connection-refuse